Mutual Hate
by mew-tsubaki
Summary: Oneshot, light slash, post-spring high prelims, pre-Winter Cup. "'I hate Oikawa.' 'No, you hate that he's flamboyant.' —Or, the fic where Iwaizumi and Kasamatsu are cousins. *Oiwa/Iwaoi, Kikasa. Light T for some language. Followed by "Crossing Paths."


**Mutual Hate**

A Haikyuu!/Kuroko no Basuke crossover

by mew-tsubaki

Note: The _Haikyuu!_ characters belong to Furudate Haruichi-sensei and the _Kuroko no Basuke_ characters to Fujimaki Tadatoshi-sensei, not to me. Honestly, I wish the sensei would just write a crossover already, because the series really could be in the same universe… ;P Read, review, and enjoy!

\- ^-^3

Iwaizumi Hajime sighs as the paper on his desk stares back up at him tauntingly. It's a short form, but it's official nevertheless. Iwaizumi grimaces and his temper flares, but all he does is crumple the paper in his hand as he grips it and stuffs it in his bag, saving it for later.

As it's lunchtime, it comes as no surprise when Oikawa sticks his head into Iwaizumi's classroom. "Iwa-chan~" he beckons.

The vice-captain frowns at his friend. "What do you want, Oikawa?" He doesn't have the strength in him to fight today.

Surprisingly, Oikawa seems to understand that. "Lunch! Did you bring yours today, or should we swing by the cafeteria?"

Iwaizumi raises an eyebrow but gets up and joins the captain anyway. "You're not eating with your groupies?" he asks while they make their way down the hall.

"Nah." Oikawa stuffs his hands in his pockets and shrugs, but he doesn't meet Iwaizumi's eyes. "Even fans tolerate a loser for only so long."

Silence settles between them, and they make it all the way to the roof without another word. There, on the roof, Kunimi and Kindaichi have secured a nice spot, and they've already started eating.

"Where are the others?" Iwaizumi asks as he and Oikawa sit.

"Yahaba-senpai has a test next period, so he's studying," Kindaichi answers. He licks some sandwich dressing from the corner of his mouth. "Watari-senpai is grabbing his lunch. Dunno where Matsukawa-senpai or Hanamaki-senpai is."

Kunimi's blank stare offers as much info as Kindaichi's words, so he silently passes Kindaichi a napkin as Kindaichi gets the rest of his lunch on himself.

Oikawa whistles. "Well…this is kinda rare, then. Just us Kitagawa Daiichi grads for once."

Kindaichi perks up at the remark. "Oh, you're right! We should do this more often, and then—" He screeches to a halt. No doubt he was going to make plans for next year.

But there is no next year, not for Oikawa, not for Iwaizumi. Hell, there's not even a next _week_ for them, because volleyball's behind them.

This path for them was secured when Karasuno beat them barely a week ago at the spring high preliminaries.

Lunch trudges on, awkwardly quiet. Watari's arrival does nothing to help, and the underclassmen rush and leave before the break's even over. It leaves Iwaizumi and Oikawa alone.

Iwaizumi glances at Oikawa—and finds the setter gazing back at him, like a bird of prey. "What?" he asks.

Oikawa's lazy smile is slow coming and not without a tinge of regret considering the former topic, but it's genuine. "Nothing."

"Then wipe that stupid smirk off your face."

"Ah, Iwa-chan. I really do love you."

Iwaizumi looks away. How can Shittykawa still go on like that? Can't he be serious even once? Can't he just cry about their loss? Iwaizumi's seen Oikawa at his best and at his worst. For once, he wishes Oikawa would be his true usual self with Iwaizumi.

But Oikawa keeps smiling. It makes staying on the roof unbearable.

"I just realized—I'm not hungry today," the vice-captain states, and he leaves.

At least Oikawa has the decency not to point out that neither of them had brought food to begin with.

\- ^-^3

The following day is the hardest.

He goes in the morning, because he's finally gathered up the courage to face their coach. Now Iwaizumi can enter the gym during morning practice without the vague feeling that he might throw up.

Irihata and Mizoguchi are sad to see him go. Irihata doesn't even look at the wrinkled resignation form, instead passing it to a frowning Mizoguchi. "You're welcome to come by whenever you have free time, Iwaizumi-kun," Irihata says gently, almost fatherly. Three years—that's all it takes to gain another parent in their coach.

Iwaizumi stares at the ground. He doesn't feel as though he has the right to look at them. "…thank you for the offer, but—"

"Don't make excuses," Irihata interrupts. "You'll burn out if all you do is study."

His stern tone lifts Iwaizumi's chin, and the former vice-captain sees pride in his coach's and his advisor's eyes. Iwaizumi may feel as though he couldn't carry the team to victory, but they certainly don't believe that.

"I'm surprised Oikawa-kun isn't with you, though," Mizoguchi comments, changing the topic.

"Knowing him, he'll be the last to resign. I bet the teachers will drag him here kicking and screaming," Iwaizumi supplies.

Irihata looks between the two of them. "Neither of you knew? Oikawa-kun was the first to retire."

Mizoguchi gapes and Iwaizumi clenches his fist. Oikawa left first? And yet—yet he still acts as though barely anything's wrong?

As if summoned by their talk, Oikawa comes prancing into the gym, all "Iwa-chan! Iwa-chan!" like some fly buzzing around Iwaizumi. Kunimi, the new vice-captain, grabs Oikawa and drags him out of the way of practice and parks him by the exit. "Don't forget to take this with you!" Kunimi calls to Iwaizumi.

Iwaizumi sighs, bows to Irihata and Mizoguchi, and is faced with bows from the remaining, active players of their team. It makes it hard to leave, but Oikawa's annoyances bring him back to reality.

"Kunimi-chan is so mean!" Oikawa whines as they head to class. "No respect for his seniors!"

The shorter male rolls his eyes. "Maybe if we'd done something worthy of respect."

Oikawa tugs on his arm and slows him until their paces match. He tries to rest his head on Iwaizumi's shoulder, despite the height difference. "You're worthy of respect and a lot more, Iwa-chan." Then his voice is right in Iwaizumi's ear, and it's not funny anymore. "That's another reason why I love you."

Iwaizumi shrugs away and smacks Oikawa with his school bag. "A-Assikawa! Knock it off, you coward! I know you retired first!"

"It's just to secure my future with you, Iwa-chan!" Oikawa calls even though Iwaizumi puts space between them in the courtyard. Other students hear Oikawa, but no one's surprised. They've had three years to get used to this.

But Iwaizumi still isn't used to it. He never has been and maybe never will be. And he kind of wishes Oikawa would knock it off. Iwaizumi hates this Oikawa Tooru. He hates this Oikawa who takes nothing seriously. He hates this Oikawa who gave up on volleyball so quickly and easily. He hates this Oikawa who can't even acknowledge that they lost and that it's over for them and that things will change even more after March when they graduate. He hates this Oikawa.

He hates Oikawa.

\- ^-^3

Iwaizumi gets a couple of days' respite. I.e., Oikawa gives him some space.

For the first time in years, Iwaizumi spends a Sunday at home and not at the volleyball club. It's an odd feeling, to say the least, and it's somewhat unnerving.

He lays out his study materials—might as well do as he's told, right?—and plans to come up with a strategy, like ten pages of history a night, along with five math and five English, or something like that.

His phone buzzes, and he thinks that maybe Oikawa really can't hold out this long without him. Except he goes to answer it and finds it's not Oikawa. "Hey, Yukio."

His cousin, barely a month younger than him, Kasamatsu Yukio, must be grinning on the other end of the line. He can hear it in his voice. "Hey, Hajime. How's everything?"

Man, Yukio has good timing. "Eh, about as well as you'd expect for a third year. You?"

"Ah, who is it?" a voice in the background asks. "Don't tell me that's Kise. Kasamatsu, you're smiling~"

There's a _**thwack**_ and a "Shut up, Moriyama!" before Yukio answers. "I guess the same. Sorry 'bout that—I'm out with my friends, Kobori and Moriyama, today, and I just remembered that I meant to call you a few days ago."

"Oh?" It wasn't as though they talked every week, but Yukio suddenly didn't sound as enthusiastic.

"Well…Auntie told Mom. Mom told me, and I remembered when I saw the volleyball magazines in a store today. I'm sorry, Hajime."

Yukio talking about their loss is okay. Not only would he have found out because of their mothers being the type of sisters to stay in touch weekly (almost daily, really), but Yukio would understand. It's all right to talk to Yukio because he plays basketball, and he lost in the Interhigh final, too. Then again, Iwaizumi lost his following tournament as well…

"Hajime?"

"I'm still here. Thanks, though." Iwaizumi runs a hand through his hair, oddly calm. "What about you? Are you done for the year?"

"You retired?" Yukio's genuinely surprised.

"Had to. The spring high was our last hurrah, and third years aren't even really expected to play in that, despite it being in January."

"I see… I'm not done," the basketball player confesses. "The Winter Cup is my last shot." Though it's unsaid, Iwaizumi can hear the "with this team that I love" at the end.

Iwaizumi whistles, impressed…and a little jealous. "Good for you, Yukio. At least you've got that ace of yours to help out. Maybe more reliable than Oikawa."

Yukio laughs. "Come on, Hajime, don't be so harsh about Tooru."

"Don't call him that. I just threw up in my mouth a little."

Iwaizumi can picture his cousin rolling his eyes. "I empathize, I do, but I guess I'm a bit biased since we'd all play together in summertime when we were little…" There's a pause. "Hmm. You've never called him anything but 'Oikawa,' though, have you?"

"I prefer 'Assikawa' or some variation."

"Oh, man… He's not that bad. He just has fans. Kise's like that, too, and he's an actual model."

"Yeah, but I think your ace isn't very bright, to be honest, based on what you've told me about him."

"No…but Kise's a good guy." Yukio pauses to curse at Moriyama again, and then the background noise grows quieter. "Sorry, I had to get away from Moriyama. He teases me incessantly about Kise. Just because I scold him all the time and look after him…" He sighs. "Well, I'd be lying if I said I hate him."

"I hate Oikawa."

"No, you hate that he's flamboyant." Yukio's voice softens. "Hajime, what's up? You sound off. And not just from your loss."

Iwaizumi bites his lower lip. Part of the reason that he and Yukio get on so well is that they think along very similar lines. Hell, one might even say that that Kise Ryouta guy is the Oikawa to Yukio's Iwaizumi. But that isn't exactly right. Iwaizumi has known Oikawa too long to like him, and he certainly doesn't return Oikawa's fake ideas of love.

"Hajime…"

"Sorry, sorry."

Yukio sighs. "What did he do this time?"

Iwaizumi grimaces. He won't sound too whiny if he tells Yukio…right? "…he quit first."

"Before you?"

"Before any of us."

"Wow." His cousin's genuinely surprised. "So…"

"I wasn't expecting that. Knowing how stubborn he is, I thought he'd be the last of us to do that." Seijou's former vice-captain takes a calming breath, but his anger quietly increases, his temples throbbing the more he thinks about how Oikawa didn't even tell him. "Honestly… I don't know what to do."

"Well, you're not really his keeper, Hajime."

"No, but I've been with him all this time. I beat it out of him in middle school, his idea of giving up when Kageyama appeared. I thought maybe that was just a fluke because someone as good as him had come along."

"So?"

"He's not someone who gives up so easily, Yukio. That's one of the reasons why we're friends. I actually admire that about him. He's ridiculously stubborn, he's annoyingly smart, and he's infuriatingly loyal."

Yukio lets him take a deep breath before replying. "Sounds like you should be telling him all this."

"I hate Oikawa," Iwaizumi insists.

"Sure you do," the basketball player says, but Iwaizumi can hear the laughter in his voice again. "But try something for once: Just ask Oikawa straight out what's on his mind. It's obvious you want to talk to him about the match and where you're going next." There are voices in the background. "Oh, sorry. I've got to go, Hajime."

"It's fine. Hey—kick ass for me at the Winter Cup, Yukio."

"Definitely."

The line disconnects, and something strikes Iwaizumi. He and his cousin have good manners but never say "goodbye." He kind of likes that. It's as if they're saying there's no need for goodbye, because they'll talk again.

Definitely.

\- ^-^3

The Winter Cup begins, but Iwaizumi returns his thoughts to his childhood friend.

Oikawa did a really good job of putting space between them, and he's even toned his personality down some at school. But that has Iwaizumi freshly worried, because what if a quieter Oikawa leads to something more disastrous than the sobbing Oikawa Iwaizumi wanted to see postgame?

He fidgets about what to do for a couple of days, and he can feel Hanamaki and Matsukawa watching the two of them like a game of Ping-Pong, wondering who'll snap first. Iwaizumi, who looks ready to burst, or Oikawa, who's fading into the muted colors of their scenery?

Neither snaps. Oikawa proposes that the four third years grab some ramen after classes—"My treat!" he insists—but Hanamaki tugs Matsukawa back and insists that the two of them have other plans. Iwaizumi asks what, and they confess they're still spending some of their free time helping out the volleyball club.

"But you guys go ahead, and maybe we'll join you later," Hanamaki finishes before he and Matsukawa head in the direction of the gym.

Oikawa buys it, but Iwaizumi watches them turn at the last second. They don't go to the gym. Man, they're bad liars.

Speaking of bad liars… "Ramen, so suddenly?" Iwaizumi prompts when he and Oikawa leave.

"Y-Yep," Oikawa forces. He smiles, but it's not as bright as it can be, and Iwaizumi goes with him to the ramen shop but, like before, he has no appetite.

They sit down and stare at their menus. The tension is thick, but Iwaizumi feels tired and he can see how worn Oikawa looks, too.

The cook looks at them, recognizes them because they come often, and takes the menus away, cooking them their usual without them even asking.

Iwaizumi glances at Oikawa. "That was unfair, you bastard," he mumbles.

Oikawa gives him a look. "Hey! What's with the name-calling?! I haven't even done or said anything!"

"It's precisely _because_ you said nothing. Are you even upset that we lost?" Uh-oh. That isn't how he meant to start this conversation.

Oikawa puffs up his chest and glares at Iwaizumi, but his eyes are wet. Oh. He really has been upset. "Of course I am!" he hisses. "Do you really think I like having lost to Tobio-chan _again_?!"

Iwaizumi pinches the bridge of his nose. Great. Is this all going to come down to Kageyama again?

But the heat in Oikawa cools, and his shoulders drop. "I didn't really think things would end this way," he mutters.

His friend's hackles go up. Oikawa never talks about things ending. "Don't talk that way."

"Well, how _am_ I allowed to talk? You don't want to hear me say most of the things that come out of my mouth—"

"Because half the time you're not being honest with yourself," Iwaizumi snaps.

The cook places two large bowls down in front of them, and the boys stare at the food, clenching their fists—Iwaizumi's on the table and Oikawa's on his lap.

"Please…," Iwaizumi says lowly. "Be yourself—your _actual_ self—with me. Bitch about everything that went wrong in that game. Blame me, blame the others. Trash-talk Karasuno, for all I care. What about Ushijima, even though he got his ass handed to him by Karasuno? Tell me about the stupid things you're doing instead of going to club or studying for entrance exams. Tell me anything except that you 'love' me."

Oikawa jolts slightly, and he moves his hands up onto the table. He grabs the handle of his spoon and swirls it in the broth, staring down at the food. "Even if that's true?"

"Especially if that's true."

"Fine." Oikawa abruptly digs in, and he points at Iwaizumi angrily with the spoon. "You're a jerk, Iwa-chan!"

Iwaizumi's blood boils, and he begins to eat, too. "You're too carefree, Shittykawa!"

"All we had to do was win that third set against Karasuno! You missed a great shot! Mad Dog-chan couldn't keep it together! Everyone was in disarray after you two! I couldn't—I couldn't do anything about that damned freckled guy's weird serve! ARGH!" Oikawa puts the spoon down and runs his hands through his hair. "Do you _know_ how awful that jump-float serve sucks?! _It sucks_! Why did they have to improve so much since we last saw them?! Why couldn't we have improved more?! Why didn't we have enough time to train Mad Dog-chan properly?! Why did we _suck_ compared to them in the end?!" He takes a breath and places his hands on the table once more. He pouts at Iwaizumi. "And I really resent the fact that you believe I'm not studying for entrance exams."

"Well, just because you quit—again, _without telling me_, I'd like to remind you—doesn't mean you aren't trolling, leading your fans on like usual or trying to turn one of them into a girlfriend." Those words, too, sound a lot harsher than Iwaizumi intends, but whatever. Oikawa's being honest, so he might as well return the favor.

The two eat in silence for a while. Then Oikawa gripes, "I _am_ studying, to get into T Uni."

Iwaizumi freezes. "No, you're not. That's my first choice."

"Well, it's my first choice, too."

The spiker gnashes his teeth at his friend. "What the hell? Another few years with you? Just great." But he's not angry anymore. And _that_ irks him.

Oikawa sticks his tongue out at him, childish as ever. "You know what? I hate you, Iwa-chan. I don't love you anymore." And he sulks into his ramen.

But the funny thing is, those are the words that put Iwaizumi at ease, and he smiles for the first time in a while.

\- ^-^3

"Have you heard back yet?" Yukio asks him in January.

"Not yet," Iwaizumi says. "I've applied to a few, though, and expect to start getting notices soon."

"Ohh! Is that Yukio-chan?" Oikawa coos from his spot on Iwaizumi's bed. He pushes the magazines he brought—too many of which feature him—out of the way to scramble up and over to Iwaizumi at his desk.

Iwaizumi shoves his hand into Oikawa's face. "Hold on." He opens the door to his room and shoves Oikawa out for a moment, locking the door behind him. Oikawa starts banging on the door, calling Iwaizumi mean and insisting he hates him, but that only makes Iwaizumi smile.

"You sound as though you're in a good mood," Yukio points out.

"I just think I've mastered being friends with Oikawa. So, you didn't get in?"

Yukio grumbles. He's been grumbling more since losing to Seirin in the Winter Cup and not being able to go to the finals, and more so since having to leave the basketball club to prepare for the university entrance exams. "No… Both Moriyama and Kobori did, and I'm jealous as hell. But I'm gonna try again." He mumbles something. "I have to keep trying, especially since even Kise is giving the club his all."

"Where are you trying for?"

"…T Uni."

Iwaizumi sighs and stifles a laugh. "Still close to Kaijou."

"Maybe Moriyama's right. Maybe I really can't leave Kise alone…" Yukio clears his throat. "What about Oikawa? Are you guys okay? I thought I heard him say he hates you just now—that's a first."

"Nah, I think I just figured out how best I like him."

"You're a sadist, Hajime."

"Hey, I _hate_ Oikawa."

Yukio snorts. "You say even though obviously you guys are still hanging out."

"Go study, Yukio. Join us at T Uni in the spring."

The basketball player sighs one last time. "Yeah, yeah… I'm just heading out from home to the library actually and—Kise?! What did you do to your hair?!"

The last thing Iwaizumi hears before Yukio accidentally hangs up is Kise saying something like, "Ehh? Doesn't senpai like it?"

Boy, Iwaizumi is glad he doesn't have a Kise in his life.

He gets up from his desk and cracks his door. Oikawa is sitting on the floor in front of it, sulking. Iwaizumi breathes a sigh of relief. He much prefers the sulking Oikawa to the one who shares his smile with everyone willy-nilly. "You can come back, you know."

"I really do hate you, Iwa-chan," Oikawa grumbles, stomping past him and flopping back on Iwaizumi's bed, making a mess and sending magazines everywhere.

Iwaizumi returns to his desk, smirking to himself. "The feeling's mutual, then."

Oikawa pouts, but Iwaizumi catches the red flush of his face and neck out of the corner of his eye, and he has to tear his eyes away before he gets embarrassed, too.

After all, the feeling may be mutual, but Iwaizumi's no longer sure which feeling that actually is.

\- ^-^3

**Hrmm… These two still like to fight me… ;P I really like the idea of Iwa-chan and Kasamatsu being cousins, though—cute. -w- Being a fan of both series, I don't think I could ever avoid the comparison between the two pairings, but they are more different than alike, I think, mostly because of the differences in Oikawa's and Kise's personalities. Anywho. I might write another in this universe sometime… I just love Iwa-chan and Kasamatsu. -w- And bloody Oiwa just being too proud to admit they actually genuinely love each other.**

**Thanks for reading, and please review! You might also enjoy my other **_**HQ!**_** fics!**

**-mew-tsubaki :]**


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